1. Field of the Invention
The present invention relates to an ink jet recording apparatus and more particularly, it relates to an ink jet recording apparatus in which a meniscus formed in the vicinity of a discharge port of an ink jet head is vibrated, and a technique for preventing clogging of the discharge port.
2. Related Background Art
An ink jet recording head of on-demand type includes a plurality of nozzle openings and pressure generating chambers communicated with the respective nozzle openings and is designed so that an ink droplet is generated by expanding and contracting the pressure generating chamber in response to a recording signal. In such a recording head, since new ink is successively supplied to the nozzle opening which is conducting a recording operation, clogging of such nozzle opening almost never occurs. However, for example, in the nozzle openings, such as an upper end nozzle opening and a lower end nozzle opening, which have less chance for discharging the ink droplets and remain in an inoperative condition, the clogging is apt to occur.
Thus, there has been proposed a so-called flushing technique in which, after the recording operation is performed continuously for a predetermined time period, the recording head is returned to capping means disposed at a non-recording area, where the ink droplets are forcibly discharged from all of the nozzle openings toward a cap by applying driving signals to piezoelectric vibrating elements.
However, in a case where such a countermeasure is considered, since the recording operation is interrupted to reduce a recording speed and consume the ink, there have been proposed many techniques in which, by applying a small driving signal which does not discharge the ink droplet to the piezoelectric vibrating element provided in the pressure generating chamber communicated with the nozzle opening which does not generate the ink droplet during the recording operation, a small vibration is applied to the meniscus in the vicinity of the nozzle opening to prevent the clogging of the nozzle opening (for example, Japanese Patent Laid-open No. 57-61576 and U.S. Pat. No. 4,350,989).
According to these techniques, although the number of the flushing operations can be decreased to thereby prevent the reduction in the recording speed and consumption of the ink, there is a problem that audible noise is generated due to the small vibration.